Wednesday, January 4, 2006

Greenland Ice Sheet melting faster than expected

Scientists have measured a significant decrease in the mass of the Greenland ice cap, using data from satellites that measures movement in Earth's mass. A team led by Dr. Isabella Velicogna of the University of Colorado, Boulder, found that Greenland's ice sheet decreased by 162 (plus or minus 22) cubic kilometers a year between 2002 and 2005. This is higher than all previously published estimates, and it represents a change of about 0.4 millimeters (.016 inches) per year to global sea level rise.

The first direct, comprehensive mass survey of the entire Greenland ice sheet updates findings published in the journal Geophysical Research Letters. Data was collected from the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (GRACE) satellite.

"Greenland hosts the largest reservoir of freshwater in the northern hemisphere, and any substantial changes in the mass of its ice sheet will affect global sea level, ocean circulation and climate," said Velicogna. "These results demonstrate Grace's ability to measure monthly mass changes for an entire ice sheet – a breakthrough in our ability to monitor such changes."

The GRACE satellites also monitor measurements of seasonal changes in the Antarctic Circumpolar Current, Earth's strongest ocean current system and a very significant force in global climate change. The scientists used techniques from meteorologists who use atmospheric pressure to estimate winds. Estimates of seasonal differences in ocean bottom pressure assisted in estimating the intensity of the deep currents that move dense, cold water away from the Antarctic. This is the first study of seasonal variability along the full length of the Antarctic Circumpolar Current, which links the Atlantic, Pacific and Indian Oceans.

The technique is a a first step in global satellite monitoring of deep ocean circulation, according to Dr. Victor Zlotnicki, an oceanographer at NASA's Jet Propulsion Laboratory. The deep ocean circulation moves heat and salt between ocean basins. The exchange of heat and salt plays an important role in weather and climate-related phenomena such as El Ninos. Some scientific studies indicate that deep ocean circulation plays a significant role in global climate change.


NASA's Grace Finds Greenland Melting Faster, 'Sees' Sumatra Quake - December 20, 2005